The hitherto unpublished German patent: application P 41 35 547 describes a gas generator for an inflatable impact cushion (airbag) for protecting an occupant of a motor vehicle from injury, in which the gas-generating material for producing gas under pressure with which the impact cushion is inflated is liquefied gas. Gas or liquefied gas generators have in principle the disadvantage that if the gas container is unsound or leaky, particularly where it is welded, gas can escape, with the result that the amount of gas or liquefied gas in the container is reduced. The gas generators may then not be operative.
It is well known to use, for example, manometers to check the pressure in a gas container. However, in the case of a container for liquefied gas this is not possible, since if a leak is present, the pressure in the gas phase, i.e. above the liquefied gas, remains almost constant.